Abstract
Magnetorheological (MR) damper-based semiactive control systems can be considered as one of the most advantageous
control systems for natural hazard mitigation in the field of civil engineering because MR dampers have many good
features such as small power requirement, reliability, and low price to manufacture. Those systems require feedback
control and power supply parts to efficiently reduce the structural responses. The control system becomes complex when
a lot of MR dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings,
resulting in difficulties in its implementation and maintenance. To overcome the above difficulties, a new-class MR
damper-based control system was recently proposed by replacing feedback control and power supply parts with an
electromagnetic induction (EMI) part consisting of permanent magnets and a coil. According to the Faraday's law of
electromagnetic induction, an EMI part produces electrical energy (i.e., electromotive force or induced voltage) from
mechanical energy (i.e., reciprocal motions of an MR damper), which is proportional to the rate of the change of the
movement of a damper. From this characteristic of an EMI part, it might be used as a response sensing device as well as
an alternative power supply. In addition, some control algorithms used in the MR damper-based semiactive control
systems require the measurement information on the response related to the relative velocity of the damper. In this study,
the sensing capability of an EMI part is preliminarily examined for an application to the MR damper-based semiactive
control system. To this end, experimental tests are carried out using the real-scale stay cable employing an MR damper
with an EMI part. It is demonstrated from the tests that an EMI part could exactly extract the dynamic characteristics of
the stay cable so that it might be used as a sensing device for estimating the tension force of the stay cable. In addition,
numerical simulations are performed to verify the control performance of the MR damper-based semiactive control
system adopting an EMI part as a power supply as well as a velocity sensor and the maximum energy dissipation
algorithm, which requires the information on the relative velocity, as a control algorithm. The numerical result validates
that the proposed control system can reduce the vibration of the stay cable effectively.
